Proportions of the Trilobe Renaissance Facades in Croatia

Nakon proporcijske analize zapadnog pročelja šibenske katedrale autor konstatira da je unatoč tomu što je prizemni dio bio izgrađen prije Jurjevog dolaska, fasada u cjelini primjer renesansnog projektiranja što se temelji na dva uspravna kvadrata (Alberti) i istostraničnog trokuta, te da su ostali elementi (trolisni zabat rozete) izvedeni iz jedinstvenog proporcijskog sustava. Fasada je primjer klasične renesanse, a da bi dokazao njezinu izuzetnu vrijednost autor komparativno analizira trolisne fasade u Osoru, Hvaru, Dubrovniku i Svetvinčentu otkrivajući ili njihovu stilsku različitost (od gotike do manirizma) ili izrazito minornu kvalitetu (Svetvinčenat).The west facade of the Šibenik cathedral has a functional three-lobed gable which is a projection of the vaults above the nave and the aisles onto the facade, a unique instance in European Renaissance architecture of the interior being identical in design to the exterior. Noting the harmonious effect of the facade, the author studies the design of its composition and analyses the system of proportions applied in order to establish whether the facade design is Renaissance in its entirety, since the lower part of the facade, up to the height of aisles, was built in the Gothic style, a decade before the arrival of Juraj the Dalmatian (1441). In the Early Renaissance period, L.B. Alberti (1470) had to solve an identical problem: to complete the facade of a Gothic church, S. Maria Novella in Florence, a part of which had already been coated in marble. Although the design of the S. Maria Novella facade is morphologically different from the Šibenik cathedral, the author points to similarities on the structural level, in the approach to the design and the proportions applied, as both architects have used the same underlying principle: two erect squares. An analysis of the proportions of the main facade of the Šibenik cathedral has led to the following conclusions. 1. The system of proportions of the facade is based on two squares: the Renaissance upper middle part of the facade can be inscribed into a square, while the total height of the facade consists of two squares. 2. The second set of linked and proportional elements is found in the trilobe facade. The semicircular central lobe and the side arcs are produced from the circles identical in radius, the centers of which are in the points of the equilateral triangle, at equal distance. Although only a half of the central circle and a sixth of the segment of the two side circles are visible, the viewer senses the relations, dimensions and classical proportions, intuitively perceiving harmony. 3. The center of the semicircular gable that crowns the facade is placed in the point of the equilateral triangle the base of which equals the total width of the facade. 4. The fourth set of proportionally linked elements in the upper Renaissance part of the facade are circular windows; the radius of the larger window equals the diameter of the smaller one whose radius again is identical to the diameter of the oculus. The circular windows are interconnected in terms of proportions which makes them appear harmonious. The diameter of the large window is nearly identical to the radius of the circle of which the central facade lobe is part. This means that the size of the largest opening is related to the already analyzed typologically linked forms - the semicircle and the segments of the three-lobed facade. In terms of style, the author points out that the portal and two windows in the lower part of the facade are markedly Gothic, while the upper Renaissance part of the facade contains only round openings. The circular opening (oculus) was introduced into the sacral architecture by Brunelleschi to become a significant element of Early Renaissance architecture. On the east part of the Šibenik cathedral the oculus is applied for the first time in the semicircular lobe of the sanctuary of the south and north aisles, completed in Juraj\u27s lifetime (1468). It has then become a legitimate solution for the transept facades, the east facade of the nave and the opposite, main facade, (completed only in the 1535.). The relief medallions in the sides of the trilobe on the unfinished facade of Alberti\u27s Tempio Malatestiano in Rimini, begun in 1446, may have been the model for the use of oculus. To establish the outstanding quality of the Šibenik cathedral composition, the author provides a comparative analysis of four Croatian churches with trilobe facades where different systems of proportions and composition achieve completely dierent visual results. a) The facade of the former Osor cathedral (1498) can be inscribed in a square and the composition structure become visible when it is divided into 16 squares (4 x 4). The side arcs of the trefoil are derived from a circle of an identical diameter, but are not 1/6 of the circle, as in Šibenik, but 1/4 and appear oversized. The trefoil gable is not added to the base square of the facade - normally a principle - but occupies one half of the entire height of the facade which therefore seems squat and clumsy. b) The facade of the Hvar cathedral (1530-1560, architect Karlić) is based on a square that encompasses the facade to the cornice and the trefoil gable is inscribed into the added half of the square. The measure unit is 1/16 of the square or a fourth of the length of its side (a/4). This measure is present in the central semicircular lobe as its radius (r=a/4), while the side lobes are 1/4 of the identical circle. The central square of the upper part of the facade is repeated twice in its lower part. The Mannerist effect of the Hvar cathedral results from its marked vertical orientation, the ratio between the upper and the lower part of the facade being 1:1 in Šibenik and 1:2 in Hvar, which changes the character of the composition. c) The proportions on the Renaissance facade of Sv Spas (Saviour) in Dubrovnik (1521, architect P. Andrijić) are submitted to a Gothic method of design and proportions derived from the diagonal section of the plane figure, leading to a gradual shortening of each compositional element. The basic square (corresponding to the ground plan of the interior bay), of the lower part of the facade, is given two additions in the upper, trilobe part, with the first forming a rectangle by a diagonal of the basic square (the side ratio 1:2), and the second 1:3. The proportional analysis of the facade indicates that the church, while built at the height of Classical Renaissance, still belongs to the combination of Gothic and Renaissance styles. d) The facade of St Mary in Svetvinčenat in Istria (1555) with its clumsy, caricature-like design and proportions is obviously a work of an unskilled, provincial builder. The facade is designed within a square divided into nine squares (3x3). The designer adhered to the coordinates but without understanding of tectonic and structural logic, as well as the principles of composition, with the result that the dimensions of the trilobe facade are inverse: the central semicircular lobe is smaller by half in diameter than the side lobes so that the tiny central part seems grotesque, flanked by two giant quarter sections. Conclusion: The Šibenik cathedral with its west facade is among the best Early Renaissance designs, and with its proportions based on two squares, one above the other, achieves a harmony that is intuitively perceived by the viewers. The composition can be defined in terms of style as a classical Renaissance work, with structural harmony and static balance typical for the visual arts of the period, and it is based on the system connecting the related parts (equal radius of the three lobes of the facade; the ratio between the rose window and the oculus is always 2:1), as well as the relationship of the parts articulating the facade with its entirety (the centers of the three circles of the gable placed in an equilateral triangle; an equilateral triangle defining the position of the lobe oculus in relation to the width of the facade). As all previous analyses of the Šibenik cathedral conducted by the author in various fields and using various means of investigation, from the identity of the material and precarved stone elements to architectural vocabulary and sculptural iconography, this analysis of its west facade proportions provides additional evidence of the unique quality of this remarkable monument of Croatian Renaissance architecture in European context